1. Field of the Invention
This invention pertains to a well pumping unit including a hydraulic linear actuator for imparting vertical reciprocating movement to a pair of cable sheaves around which pump rod lift cables are trained and anchored at their respective opposite ends to the pump rod and the pumping unit frame.
2. Background Art
In the art of oil well pumping units there has been a continuing need for compact and mechanically uncomplicated equipment which may be easily transported to and from the well site and which is sufficiently reliable to permit automatic unattended operation for long periods of time. The most widely accepted type of well pumping equipment for some time has been the traditional rocking or walking beam type unit which, although somewhat reliable, is relatively heavy and mechanically complicated, requiring considerable mechanical linkage and relatively moving parts which require lubrication.
Moreover, heretofore known types of well pumping equipment have lacked the flexibility for adjustment of the length of the pump stroke of the well pumping mechanism. There has been an increasing need for well pumping units which may be readily adjusted to vary the length of stroke of the polished rod and the sucker rod pump mechanism connected thereto. The increased pumping of partially depleted fields and fields having deposits of relatively heavy crude oil has resulted in a substantial need for equipment which provides a relatively long sucker rod actuating stroke and which also is readily adjustable to vary the stroke length in accordance with the pumping requirements of a particular well.
Another problem in the art of well pumping equipment pertains to the overall reliability of the pumping unit. The increasing reliability of hydraulic power supply systems has made it desirable to pursue the development of well pumping equipment which may utilize hydraulic system components for the development of compact and efficient pump actuating mechanisms. The further need for increased reliability of well pumping units requires that the mechanism be mechanically uncomplicated and have a minimum number of components which require periodic lubrication.
The above noted requirements in the art of well pump actuating equipment have been heretofore difficult to meet while at the same time providing a unit which is compact, lightweight and easily transported to and from the well site as well as being adapted for easy servicing of the well and the pump actuating mechanism itself.